1. Field of the Invention
This invention relates generally to methods and apparatus for drilling and completing subterranean wells and, more particularly, to methods and apparatus for a drillable bridge plug and other related downhole apparatus.
2. Description of Related Art
There are many applications in well drilling, servicing, and completion in which it becomes necessary to isolate particular zones within the well. In some applications, such as cased-hole situations, conventional bridge plugs such as the Baker Hughes model T, N1, NC1, P1, or S wireline-set bridge plugs are inserted into the well to isolate zones. The bridge plugs may be temporary or permanent; the purpose of the plugs is simply to isolate some portion of the well from another portion of the well. In some instances perforations in the well in one portion need to be isolated from perforations in another portion of the well. In other situations there may be a need to use a bridge plug to isolate the bottom of the well from the wellhead. There are also situations where these plugs are not used necessarily for isolation but instead are used to create a cement plug in the wellbore which may be used for permanent abandonment. In other applications a bridge plug with cement on top of it may be used as a kickoff plug for side-tracking the well.
Bridge plugs may be drillable or retrievable. Drillable bridge plugs are typically constructed of a brittle metal such as cast iron that can be drilled out. One typical problem with conventional drillable bridge plugs is that without some sort of locking mechanism, the bridge plug components tend to rotate with the drill bit, which may result in extremely long drill-out times, excessive casing wear, or both. Long drill-out times are highly undesirable as rig time is typically charged for by the hour.
Another typical problem with conventional drillable plugs is that the conventional metallic construction materials, even though brittle, are not easy to drill through. The plugs are generally required to be quite robust to achieve an isolating seal, but the materials of construction may then be difficult to drill out in a reasonable time. These typical metallic plugs thus require that significant weight be applied to the drill-bit in order to drill the plug out. It would be desirable to create a plug that did not require significant forces to be applied to the drill-bit such that the drilling operation could be accomplished with a coiled tubing motor and bit; however, conventional metallic plugs do not enable this.
In addition, when several plugs are used in succession to isolate a plurality of zones within the wellbore, there may be significant pressures on the plug from either side. It would be desirable to design an easily drilled bridge plug that is capable of holding high differential pressures on both sides of the plug. Also, with the potential for use of multiple plugs in the same wellbore, it would be desirable to create a rotational lock between plugs. A rotational lock between plugs would facilitate less time-consuming drill outs.
The present invention is directed to overcoming, or at least reducing the effects of, one or more of the issues set forth above.
In one embodiment a subterranean apparatus is disclosed. The apparatus may include a mandrel having an outer surface and a non-circular cross-section and a packing element arranged about the mandrel, the packing element having a non-cylindrical inner surface such that rotation between the mandrel and the packing element is precluded. The mandrel may include non-metallic materials, for example carbon fiber.
In one embodiment, the apparatus exhibits a non-circular cross-section that is hexagonally shaped. The interference between the non-circular outer surface of the mandrel and the inner surface of the packing element comprise a rotational lock.
In one embodiment the apparatus includes an anchoring assembly arranged about the mandrel, the anchoring assembly having a non-circular inner surface such that rotation between the mandrel and the anchoring assembly is precluded. The anchoring assembly may further include a first plurality of slips arranged about the non-circular mandrel outer surface, the slips being configured in a non-circular loop such that rotation between the mandrel and the slips is precluded by interference between the loop shape and the mandrel outer surface shape. The first plurality of slips may include non-metallic materials. The first plurality of slips may each include a metallic insert mechanically attached to and/or integrally formed into each of the plurality of slips wherein the metallic insert is engagable with a wellbore wall. The anchoring assembly may also include a first cone arranged about the mandrel, the first cone having a non-circular inner surface such that rotation between the mandrel and the first cone is precluded by interference between the first cone inner surface shape and the mandrel outer surface shape. The first plurality of slips abuts the first cone, facilitating radial outward movement of the slips into engagement with a wellbore wall upon traversal of the plurality of slips along the first cone. In is this embodiment, the first cone may include non-metallic materials. At least one shearing device may be disposed between the first cone and the mandrel, the sharing device being adapted to shear upon the application of a predetermined force.
The anchoring assembly of the apparatus may further include a second plurality of slips arranged about the non-circular outer surface of the mandrel, the second plurality of slips, the slips being configured in a non-circular loop such that rotation between the mandrel and the slips is precluded by interference between the loop shape and the mandrel outer surface shape. The second plurality of slips may include non-metallic materials. The second plurality of slips may each include a metallic insert mechanically attached to and/or integrally formed therein with the metallic inserts being engagable with the wellbore wall. The anchoring assembly may also include a second collapsible cone arranged about the non-circular outer surface of the mandrel, the second collapsible cone having a non-circular inner surface such that rotation between the mandrel and the second cone is precluded by interference between the second cone inner surface shape and the mandrel outer surface shape, wherein the second plurality of slips abuts the second collapsible cone, facilitating radial outward movement of the slips into engagement with the wellbore wall upon traversal of the plurality of slips along the second collapsible cone. The second collapsible cone may include non-metallic materials. The second collapsible cone may be adapted to collapse upon the application of a predetermined force. The second collapsible cone may include at least one metallic insert mechanically attached to and/or integrally formed therein, the at least one metallic insert facilitating a locking engagement between the cone and the mandrel. The anchoring assembly may include at least one shearing device disposed between the second collapsible cone and the mandrel, the at least one shearing device being adapted to shear upon the application of a predetermined force.
In one embodiment the packing element is disposed between the first cone and the second collapsible cone. In one embodiment a first cap is attached to a first end of the mandrel. The first cap may include non-metallic materials. The first cap may be attached to the mandrel by a plurality of non-metallic pins.
In one embodiment the first cap may abut a first plurality of slips. In one embodiment the packing element includes a first end element, a second end element, and a elastomer disposed therebetween. The elastomer may be adapted to form a seal about the non-circular outer surface of the mandrel by expanding radially to seal with the wall of the wellbore upon compressive pressure applied by the first and second end elements.
In one embodiment the apparatus may include a second cap attached to a second end of the mandrel. The second cap may include non-metallic materials. The second cap may be attached to the mandrel by a plurality of non-metallic pins. In this embodiment, the second cap may abut a second plurality of slips. In one embodiment the first end cap is adapted to rotationally lock with a second mandrel of a second identical apparatus such as a bridge plug.
In one embodiment the apparatus includes a hole in the mandrel extending at least partially therethrough. In another embodiment the hole extends all the way through the mandrel. In the embodiment with the hole extending all the way therethrough, the mandrel may include a valve arranged in the hole facilitating the flow of cement or other fluids, gases, or slurries through the mandrel, thereby enabling the invention to become a cement retainer.
In one embodiment there is disclosed a subterranean apparatus including a mandrel having an outer surface and a non-circular cross-section, and an anchoring assembly arranged about the mandrel, the anchoring assembly having a non-circular inner surface such that rotation between the mandrel and the anchoring assembly is precluded as the outer surface of the mandrel and inner surface of the packing element interfere with one another in rotation.
In one embodiment there is disclosed a subterranean apparatus including a mandrel; a first cone arranged about an outer diameter of the mandrel; a first plurality of slips arranged about first cone; a second cone spaced from the first cone and arranged about the outer diameter of the mandrel; a second plurality of slips arranged about the first cone; a metallic insert disposed in an inner surface of the second cone and adjacent to the mandrel; a packing element disposed between the first and second cones; with the first and second pluralities of slips being lockingly engagable with the wall of a wellbore and the metallic insert being lockingly engagable with the mandrel. In this embodiment the second cone may be collapsible onto the mandrel upon the application of a predetermined force. The mandrel, cones, and slips may include non-metallic materials. In addition, a cross-section of the mandrel is non-circular and the inner surfaces of the cones, slips, and packing element are non-circular and may or may not match the outer surface of the mandrel.
In one embodiment there is disclosed a slip assembly for use on subterranean apparatus including: a first cone with at least one channel therein; a first plurality of slips, each having an attached metallic insert, the first slips being arranged about the first cone in the at least one channel of the first cone; a second collapsible cone having an interior surface and an attached metallic insert disposed in the interior surface; a second plurality of non-metallic slips, each having an attached metallic insert, the second slips being arranged about the second cone; with the second non-metallic collapsible cone being adapted to collapse upon the application of a predetermined force. In this embodiment the first and second pluralities of slips are adapted to traverse first and second cones until the slips lockingly engage with a wellbore wall. The insert of the second non-metallic cone is adapted to lockingly engage with a mandrel upon the collapse of the cone. Each of first and second cones and first and second pluralities of slips may include non-metallic materials.
There is also disclosed a method of plugging or setting a packer in a well. The method may include the steps of: running an apparatus into a well, the apparatus comprising a mandrel with a non-cylindrical outer surface and a packing element arranged about the mandrel; setting the packing element by the application force delivered from conventional setting tools and means including, but not limited to: wireline pressure setting tools, mechanical setting tools, and hydraulic setting tools; locking the apparatus in place within the well; and locking an anchoring assembly to the mandrel. According to this method the apparatus may include a first cone arranged about the outer surface of the mandrel; a first plurality of slips arranged about the first cone; a second cone spaced from the first cone and arranged about the outer diameter of the mandrel; a second plurality of slips arranged about the second cone; a metallic insert disposed in an inner surface of the second cone and adjacent to the mandrel; with the first and second pluralities of slips being lockingly engagable with the wall of a wellbore and the metallic insert being lockingly engagable with the mandrel. The first and second cones may include a plurality of channels receptive of the first and second pluralities of slips. Also according to this method, the step of running the apparatus into the well may include running the apparatus such as a plug on wireline. The step of running the apparatus into the well may also include running the apparatus on a mechanical or hydraulic setting tool. The step of locking the apparatus within the well may further include the first and second pluralities of slips traversing the first and second cones and engaging with a wall of the well. The step of locking the anchoring assembly to the mandrel may further include collapsing the second cone and engaging the second cone metallic insert with the mandrel.
There is also disclosed a method of drilling out a subterranean apparatus such as a plug including the steps of: running a drill into a wellbore; and drilling the apparatus; where the apparatus is substantially non-metallic and includes a mandrel having a non-cylindrical outer surface; and a packing element arranged about the mandrel, the packing element having a non-cylindrical inner surface matching the mandrel outer surface. According to this method, the step of running the drill into the wellbore may be accomplished by using coiled tubing. Also, drilling may be accomplished by a coiled tubing motor and bit.
In one embodiment there is disclosed an adapter kit for a running a subterranean apparatus including: a bushing adapted to connect to a running tool; a setting sleeve attached to the bushing, the setting sleeve extending to the subterranean apparatus; a setting mandrel interior to the setting sleeve; a support sleeve attached to the setting mandrel and disposed between the setting mandrel and the setting sleeve; and a collet having first and second ends, the first end of the collet being attached to the setting mandrel and the second end of the collet being releasably attached to the subterranean apparatus. According to this adapter kit the subterranean apparatus may include an apparatus having a packing element and an anchoring assembly. The subterranean apparatus may include a plug, cement retainer, or packer. The anchoring assembly may be set by the transmission of force from the setting sleeve to the anchoring assembly. In addition, the packing element may be set by the transmission of force from the setting sleeve, through the anchoring assembly, and to the packing element. According to this embodiment the collet is locked into engagement with the subterranean apparatus by the support sleeve in a first position. The support sleeve first position may be facilitated by a shearing device such as shear pins or shear rings. The support sleeve may be movable into a second position upon the application of a predetermined force to shear the shear pin. According to this embodiment, the collet may be unlocked from engagement with the subterranean apparatus by moving the support sleeve to the second position.
In one embodiment there is disclosed a bridge plug for use in a subterranean well including: a mandrel having first and second ends; a packing element; an anchoring assembly; a first end cap attached to the first end of the mandrel; a second end cap attached to the second end of the mandrel; where the first end cap is adapted to rotationally lock with the second end of the mandrel of another bridge plug. According to this embodiment, each of mandrel, packing element, anchoring assembly, and end caps may be constructed of substantially non-metallic materials.
In some embodiments, the first and/or the second plurality of slips of the subterranean apparatus include cavities that facilitate the drilling out operation. In some embodiments, these slips are comprised of cast iron.